Effective hair spray formulations and film forming resins must meet a rigid set of requirements. Specifically, the film forming resins should remain non-tacky in a humid environment but be easily removed using soap solutions such as shampoos. The film should have high hair cohesivity and posses sufficient strength and elasticity so as to avoid dusting or flaking when the hair is subjected to combing or brushing stresses, and remain clear, transparent and glossy on aging. The film forming resin should have a viscosity range which permits spraying without nozzle clogging, and should show little or no tendency to interact with perfumes or other optional components typically utilized in a hair spray formulation. The resin should also be readily soluble in various solvents while exhibiting good compatibility with conventional propellants such as hydrocarbon propellants, dimethyl ether propellants, or mixtures thereof.
Many polymeric systems have been developed in an attempt to meet these stringent requirements. Among these are polyvinylpyrrolidone and co-polymers of N-vinylpyrrolidone with vinyl acetate. However, these co-polymers do not exhibit the desired degree of holding under high humidity conditions. Moreover, several of the vinylpyrrolidone polymers possess an unpleasant odor. Methyl vinyl ether/maleic acid half ester co-polymers have also been used in hair sprays but must be of a relatively high molecular weight to achieve adequate holding. Vinyl acetate polymers having 15 to 35 percent of their acetate groups converted to hydroxyl groups have been proposed for increased solubility in carbon dioxide propellant systems. However such increased solubility is achieved at the cost of lowered holding power. While each of the above resins meets at least some of the above cited requirements, none exhibits all of these characteristics to a satisfactory degree.
In U.S. Pat. No. 4,689,379, a terpolymer resin of random or alternating structure is discussed comprising essentially a vinyl ester, a water insoluble or water miscible alkyl maleate half ester and the acrylate or methacrylate ester of a saturated hydroxylated bicyclic hydrocarbon in a molar ratio of about 1 to 0.35-1 to 0.05-0.25. Preferably, the resin is prepared in the form of beads or microspheres by suspension polymerization to provide a higher molecular weight for better hair holding under humid conditions. The terpolymers are preferably composed of vinyl acetate, an alkyl maleate half ester and acrylate and/or methacrylate esters of isoborneol, exo-norborneol and endonorborneol, with the isoborneol ester most preferred.
While useful in the preparation of hair treating formulations and hair sprays, additional advances in the art continue to be sought.